Chip package and fabrication method thereof

ABSTRACT

The invention provides a chip package and fabrication method thereof. In one embodiment, the chip package includes: a semiconductor substrate having opposite first and second surfaces, at least one bond pad region and at least one device region; a plurality of conductive pad structures disposed on the bond pad region at the first surface of the semiconductor substrate; a plurality of heavily doped regions isolated from one another, underlying and electrically connected to the conductive pad structures; and a plurality of conductive bumps underlying the heavily doped regions and electrically connected to the conductive pad structures through the heavily-doped regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/788,091 filed on May 26, 2010, which claims priority of ProvisionalU.S. Patent Application Nos. 61/235,146 and 61/235,153, both filed onAug. 19, 2009, the entirety of which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a chip package, and in particular, to awafer-level chip package and fabrication method thereof.

2. Description of the Related Art

A wafer level packaging technique for chip packaging has been developed.A wafer level package is first completed and then a dicing step isperformed to form separated chip packages. A redistribution pattern in achip package is mainly designed to be in direct contact with metal pads.Thus, the process for forming the redistribution pattern must correspondwith the design of the metal pads.

It is desired to have a novel chip package and a fabrication methodthereof to address the above issues.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the invention, a chip package is provided. Anexemplary chip package comprises: a semiconductor substrate havingopposite first and second surfaces, at least one bond pad region, and atleast one device region; a plurality of conductive pad structuresdisposed on the bond pad region at the first surface of thesemiconductor substrate; a plurality of heavily doped regions isolatedfrom one another, underlying and electrically connected to theconductive pad structures; and a plurality of conductive bumpsunderlying the heavily doped regions and electrically connected to theconductive pad structures through the heavily doped regions.

According to another aspect of the invention, a method for fabricating achip package is provided. An exemplary method comprises: providing asemiconductor wafer having opposite first and second surfaces, whereinthe semiconductor wafer comprises at least one bond pad region, at leastone device region, and a plurality of conductive pad structures on thefirst surface and disposed on the bond pad region; forming a pluralityof heavily doped regions underlying the conductive pad structures,wherein the heavily-doped regions are isolated from one another andelectrically connected to the conductive pad structures; and forming aplurality of conductive bumps underlying the heavily-doped regions,wherein the conductive bumps are electrically connected to theconductive pad structures through the heavily doped regions.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIGS. 1-2 are cross sections showing a method for fabricating asemiconductor chip according to an embodiment of the invention;

FIGS. 3A-3F are cross sections showing a method for fabricating acarrier wafer according to another embodiment of the invention;

FIGS. 4-5 are cross sections showing a method for fabricating asemiconductor chip according to another embodiment of the invention;

FIGS. 6A-6B are cross sections showing a method for fabricating asemiconductor chip according to yet another embodiment of the invention;

FIGS. 7A-7D are cross sections showing a method for fabricating asemiconductor chip according to a further embodiment of the invention;and

FIGS. 8A-8D are cross sections showing a method for fabricating asemiconductor chip according to a still further embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

In the drawings or the description, similar or same reference numeralsare used to designate similar or same elements. In addition, shapes orthickness of elements shown in the drawings may be exaggerated forclarity or simplicity. Further, each element shown in the drawings willbe described. It should be understood that any element not shown ordescribed may be any kind of conventional element as known by thoseskilled in the art. In addition, the disclosed embodiment is merely aspecific example for practicing the invention, without acting as alimitation upon its scope.

A CMOS image sensor device package is used as an example. However, amicro-electromechanical system (MEMS) chip package or othersemiconductor chips may also be suitable for use. That is, it should beappreciated that the chip package of the embodiments of the inventionmay be applied to electronic components with active or passive devices,or digital or analog circuits, such as opto electronic devices,micro-electromechanical systems (MEMS), micro fluidic systems, andphysical sensors for detecting heat, light, or pressure. Particularly, awafer scale package (WSP) process may be applied to packagesemiconductor chips, such as image sensor devices, light-emitting diodes(LEDs), solar cells, RF circuits, accelerators, gyroscopes, microactuators, surface acoustic wave devices, pressure sensors, or inkprinter heads.

The wafer scale package process mentioned above mainly means that afterthe package process is accomplished during the wafer stage, the waferwith chips is cut to obtain separate independent packages. However, in aspecific embodiment, separate independent chips may be redistributedoverlying a supporting wafer and then be packaged, which may also bereferred to as a wafer scale package process. In addition, the abovementioned wafer scale package process may also be adapted to form chippackages of multi-layer integrated circuit devices by stacking aplurality of wafers having integrated circuits.

According to a feature of the invention, the electrical connectionsbetween conductive pad structures and conductive bumps are achieved bythe use of heavily doped regions. As such, it is not necessary for aredistribution pattern to be in direct contact with conductive padstructures. In one embodiment, the heavily doped regions are disposed inthe semiconductor substrate underlying the conductive pad structures. Inanother embodiment, the heavily doped regions are disposed in a carriersubstrate bonded to the semiconductor substrate.

Referring to FIGS. 1-2, cross-sectional views illustrating the steps forforming a chip package on a semiconductor wafer according to anembodiment of the invention are shown. In this embodiment, the heavilydoped regions are disposed in the semiconductor substrate underlying theconductive pad structures. As shown in FIGS. 1-2, a semiconductor wafer300 is first provided, which is typically a silicon wafer. Thesemiconductor wafer includes an insulating layer 301, which may beformed by semiconductor processing steps such as a thermal oxidation orchemical vapor deposition step. In one embodiment, asilicon-on-insulator (SOI) substrate may be used. Alternatively, thesemiconductor wafer may be formed by combing two wafers together, usinga wafer bonding process, wherein one of the wafers is provided with aninsulating layer. The semiconductor wafer are defined with a pluralityof device regions 100A surrounded by peripheral bonding pad regions100B. Thereafter, insulating walls 305 connecting to the insulatinglayer 301 are formed in the semiconductor wafer 300 to isolate aplurality of regions as heavily doped regions 300B. A semiconductordevice 302 such as an image sensor device or MEMS is fabricated in thedevice region 100A. Overlying the semiconductor wafer 300 and thesemiconductor device 302 is an intermetal dielectric (IMD) layer 303,which is typically a low-k dielectric such as porous oxide. A pluralityof conductive pad structures 304 are fabricated in the IMD layer 303 onthe peripheral bonding pad regions 100B. The insulating walls and theinsulating layer may be formed of an insulating material such as siliconoxide, or an insulation space such as air gap or vacuum. The conductivepad structures 304 are preferably made of materials such as copper (Cu),aluminum (Al), or other suitable metals. It should be noted that thesemiconductor wafer comprises a plurality of heavily doped region 300Bin the peripheral bonding pad regions 100B, wherein the heavily dopedregions 300B are isolated by insulating walls 305 and electricallyconnected to the conducive pad structures 304. The heavily doped regions300B may be formed by doping ions (e.g., phosphors or arsenic ions) of ahigh concentration (e.g., 1E14-6E15 atoms/cm²) by, for example,diffusion or ion implantation processes, to form a conductive path. Inan embodiment, one heavily doped region corresponds to one conductivepad structure. However, when a plurality of conductive pad structuresare used as a common output, one heavily doped region may correspond toa plurality of conductive pad structures at the same time.

In addition, the semiconductor wafer 300, produced by wafer foundries,may be covered with a chip passivation layer 306. Meanwhile, in order toelectrically connect the devices in the chip to external circuits, thechip passivation layer 306 may be defined in advance by wafer foundriesto form a plurality of openings 306 h exposing the conductive padstructures 304.

Next, as shown in FIG. 3A, a packaging layer 500 is bonded to thesemiconductor wafer. For simplicity, only the conductive pad structures304, the insulating walls 305, and the insulating layer 301 are shown inthe semiconductor wafer 300. The packaging layer 500 may be, forexample, a transparent substrate such as glass, another blank siliconwafer, or another wafer having integrated circuits. In one embodiment, aspacer layer 310 is used to separate the packaging layer 500 and thesemiconductor substrate such that a cavity 316 surrounded by the spacerlayer 310 is formed. The spacer layer 310 may be a sealant resin or aphotosensitive insulating material, such as epoxy, solder mask, and soon. In addition, the spacer layer 310 may be formed on the semiconductorwafer 300, and then bonded with the opposing packaging layer 500 usingan adhesion layer. On the other hand, the spacer layer 310 may also beformed on the packaging layer 500, and then bonded with an opposingsemiconductor substrate 300 using an adhesion layer.

Referring to FIG. 3B, using the packaging layer 500 as a supportingsubstrate, the backside 300 a of the semiconductor wafer is etched by,for example, an anisotropic etch process, to remove portions of thesemiconductor wafer 300 and the insulating layer 301 to form openings300 h therethrough to expose the heavily doped regions 300B. It shouldbe noted that each of the openings 300 h corresponds to the heavilydoped regions 300B in the peripheral bonding pad regions 100B isolatedby the insulating walls 305.

As shown in FIG. 3C, an insulating layer 320 which exposes the heavilydoped regions 300B is formed in the openings 300 h. The insulating layer320 may be a silicon oxide layer formed by thermal oxidation or plasmachemical vapor deposition processes. For example, the insulating layer320 may be formed in the openings 300 h and extend to the backside 300 aof the semiconductor wafer 300, and then the portion of the insulatinglayer at the bottom of the openings 300 h would be removed byconventional photolithography and etching processes to expose theheavily doped regions 300B.

Next, as shown in FIG. 3D, a conductive pattern 330 is formed in theopenings 300 h. In this embodiment, the conductive pattern serves as aredistribution pattern and therefore, the conductive pattern is formedon the sidewalls of the openings 300 h and further extended to thebottom surface 300 a of the semiconductor wafer 300 a and the heavilydoped regions 300B. The redistribution pattern 330 may be formed byphysical vapor deposition, chemical vapor deposition, electroplating,and eletroless plating processes, and so on. The redistribution pattern330 may be formed of metals such as copper, aluminum, gold, orcombinations thereof. Alternatively, the redistribution pattern 330 maybe formed of conductive oxides such as indium tin oxide (ITO), indiumzinc oxide (IZO), or a combination thereof. In one embodiment, aconductive layer is conformally formed on the entire semiconductorwafer, and then patterned to form the redistribution pattern as shown inFIG. 3D.

Thereafter, referring to FIG. 3E, the formation of a passivation layer340 is shown. In an embodiment of the invention, the passivation layer340 may, for example, be a solder mask. A solder mask material may beapplied overlying the backside 300 a of the semiconductor wafer to formthe passivation layer 340. Then, the passivation layer 340 is patternedto form a plurality of terminal contact openings, exposing portions ofthe redistribution pattern 330. Then, an under bump metallurgy (UBM) anda conductive bump 350 are formed at the terminal contact openings. Forexample, the UBM may be formed of a conductive material such as a metalor metal alloy, and may be nickel, silver, aluminum, cooper, or alloysthereof. Alternatively, the UBM may be a doped polysilicon, singlecrystalline silicon, or conducting glass layer. In addition, arefractory metal material such as titanium, molybdenum, chromium, ortitanium-tungsten layer may be used alone or in combination with othermetal layers. In a specific embodiment, a nickel/gold layer may bepartially or entirely formed overlying a surface of the metal layer.Through the redistribution pattern 330, the conductive bumps 350 may beelectrically connected to the heavily doped regions 300B instead of theconductive pad structures 304. In an embodiment of the invention, theconductive bump 350 is used to transmit input/output (I/O), ground, orpower signals of the device 302. Subsequently, the semiconductor waferis diced along the scribe line SC on the peripheral bonding pad region,to thereby form a plurality of chip packages.

The heavily doped regions 300B in the peripheral bonding pad regions areisolated by the insulating walls 305. Therefore, the redistributionpattern 330 can electrically connect to the heavily doped regions 300B,and it is not necessary for the redistribution pattern to be in directcontact with the conductive pad structures 304. In addition, the heavilydoped regions 300B in the peripheral bonding pad regions may have anarea that is wider than that of the conductive pad structures 304 suchthat the contact openings 300 h have a larger process window foralignment.

Furthermore, as shown in FIG. 3F, the depth of the opening 300 h maypenetrate beyond the insulating layer 301 such that the redistributionpattern 330 may extend into the heavily doped regions 300B, or evenreach the conductive pad structures 304 to thereby increase the contactarea. In other words, the insulating layer 301 may be at the bottom ofthe openings 300 h or below the openings.

Referring to FIGS. 4-5, cross-sectional views illustrating the steps forforming a chip package on a semiconductor wafer according to anotherembodiment of the invention are shown. In this embodiment, the heavilydoped regions are disposed in a carrier substrate. As shown in FIGS.4-5, a semiconductor wafer 300 is first provided, which is typically asilicon wafer. The semiconductor wafer includes an upper surface 300 aand a bottom surface 300 b. In addition, a plurality of scribe lineregions and substrates corresponding to chips are defined in thesemiconductor wafer, wherein each of the chips includes at least onedevice region 100A surrounded by a peripheral bonding pad region 100B.Thereafter, a semiconductor device 302 such as an image sensor device orMEMS is fabricated on the upper surface 300 a in the device region 100A.Overlying the semiconductor wafer 300 and the semiconductor device 302is an intermetal dielectric (IMD) layer 303, which is typically a low-kdielectric such as porous oxide. A plurality of conductive padstructures 304 are fabricated in the IMD layer 303 on the peripheralbonding pad region 100B. The conductive pad structures 304 arepreferably made of materials such as copper (Cu), aluminum (Al), orother suitable metals.

In addition, the semiconductor wafer 300, produced by wafer foundries,may be covered with a chip passivation layer 306. Meanwhile, in order toelectrically connect the devices in the chip to external circuits, thechip passivation layer 306 may be defined in advance by wafer foundriesto form a plurality of openings 306 h exposing the conductive padstructures 304.

Next, as shown in FIG. 6A, a semiconductor wafer 600 such as a blanksilicon wafer or a silicon wafer with integrated circuits is provided asa carrier substrate, which includes an upper surface 600 a and a bottomsurface 600 b. A plurality of openings 600 h are formed by removingportions of the semiconductor wafer 600 from the upper surface 600 a.The openings 600 h are then filled with insulating layers 610, forexample, formed of polymer materials such as polyimide. Alternatively,an insulating layer such as silicon oxide may be formed by semiconductorprocessing steps. For example, a silicon oxide layer is blanketly formedby thermal oxidation or plasma chemical vapor deposition processes, andthereafter, the oxide layer on the upper surface 600 a and/or bottomsurface 600 b of the silicon wafer 600 may be removed. It should benoted that the silicon wafer 600 is a heavily doped substrate, which maybe formed by doping ions (e.g., phosphors or arsenic ions) of a highconcentration (e.g., 1E14-6E15 atoms/cm2) by, for example, diffusion orion implantation processes, to form a conductive path. In an embodiment,one heavily doped region corresponds to one conductive pad structure.However, when a plurality of conductive pad structures are used as acommon output, one heavily doped region may correspond to a plurality ofconductive pad structures at the same time.

Referring to FIG. 7A, the semiconductor substrate 300 with asemiconductor device is bonded to the carrier substrate 600. Forexample, the semiconductor substrate 300 is flipped upside down with itsupper surface 300 a bonded to the upper surface 600 a of the carriersubstrate 600 such that the semiconductor device 302 is away from thecarrier substrate 600, while the conductive pad structures 304 arefacing and bonded to the upper surface 600 a of the carrier substrate600. For simplicity, only the conductive pad structures 304, thesemiconductor device 302, and the IMD layer 303 are shown in thesemiconductor substrate 300.

Thereafter, as shown in FIG. 7B, the semiconductor substrate 300 isthinned from the bottom surface 300 b thereof (as indicated by the dashlines) to a suitable thickness by, for example, etching, milling,grinding, or polishing processes. For example, when the semiconductordevice is an image sensor, the thinned silicon substrate 300 should bethin enough to permit a sufficient amount of light to pass therethroughfor the image sensor 302 to sense incident light and generate signals.In this embodiment, the bottom surface 300 b of the semiconductorsubstrate 300 is used as a light incident surface.

After completion of the thinning process, a packaging layer 500 isbonded to the bottom surface 300 b of the semiconductor wafer 300, asshown in FIG. 7C. The packaging layer may be for example, a transparentsubstrate such as glass, another blank silicon wafer, or another waferhaving integrated circuits. In one embodiment, a spacer layer 310 isused to separate the packaging layer 500 and the semiconductor substratesuch that a cavity 316 surrounded by the spacer layer 310 is formed. Thespacer layer 310 may be a sealant resin or a photosensitive insulatingmaterial, such as epoxy, solder mask, and so on. In addition, the spacerlayer 310 may be formed on the bottom surface 300 b of the siliconsubstrate 300, and then bonded with the opposing packaging layer 500using an adhesion layer. On the other hand, the spacer layer 310 mayalso be formed on the packaging layer 500, and then bonded with anopposing bottom surface 300 b of the silicon substrate 300 using anadhesion layer.

FIG. 7D illustrates an optional process, wherein the carrier substrateis thinned from the bottom surface 600 b thereof, using the packaginglayer 500 as a supporting substrate. For example, the backside 600 b ofthe carrier substrate is polished by a chemical mechanical polishingprocess to expose surfaces of the insulating layers 610 such that theinsulating layers constitute an insulating wall 610 to isolate theheavily doped regions 600B in the carrier substrate 600 which correspondto the peripheral bonding pad regions 100B.

Thereafter, a passivation layer 640 is formed. In an embodiment of theinvention, the passivation layer 640 may, for example, be a solder mask.A solder mask material may be applied overlying the bottom surface 600 bof the carrier substrate 600 b to form the passivation layer 640. Then,the passivation layer 640 is patterned to form a plurality of contactopenings, exposing portions of the bottom surface 600 b of the carriersubstrate. Then, an under bump metallurgy (UBM) and a conductive bump350 are formed at the contact openings. For example, the UBM may beformed of a conductive material such as a metal or metal alloy, and maybe nickel, silver, aluminum, cooper, or alloys thereof. Alternatively,the UBM may be a doped polysilicon, single crystalline silicon, orconducting glass layer. In addition, a refractory metal material such astitanium, molybdenum, chromium, or titanium- tungsten layer may be usedalone or in combination with other metal layers. In a specificembodiment, a redistribution pattern can be used to redistribute theposition of the conductive bump 650.

In an embodiment of the invention, the conductive bump 650 is used totransmit input/output (I/O), ground, or power signals of the device 302.Subsequently, the semiconductor wafer is diced along the scribe line SCon the peripheral bonding pad region, to thereby form a plurality ofchip packages.

In addition, the heavily doped regions 600B in the carrier substrate 600which correspond to the peripheral bonding pad region are isolated bythe insulating wall 610. Therefore, the conductive bumps 650 canelectrically connect to the heavily doped regions 600B by direct contactor by the redistribution pattern. It is not necessary for the conductivebumps 650 to be in direct contact with the conductive pad structures304. In addition, the heavily doped regions 600B in the carriersubstrate 600 which correspond to the peripheral bonding pad regions mayhave an area that is wider than that of the conductive pad structuressuch that the contact openings have a larger process window foralignment.

Referring to FIGS. 8A-8D, cross-sectional views showing the steps forforming a chip package according to another embodiment of the inventionare shown, wherein a primary difference with the previous embodiment isthat the carrier substrate 600 is a silicon-on-insulator (SOI) substratewhich includes an insulating layer 630. Insulating walls 610 extendingto the insulating layer 630 are formed in the carrier substrate 600 toisolate the heavily doped regions 600B which correspond to theperipheral bonding pad regions 100B. The insulating walls and theinsulating layer may be formed of silicon oxide. The heavily dopedregions 600B may be formed by an ion implantation process, which may beperformed before or after the formation of the insulating walls 610.Next, as shown in FIG. 8B, a portion of thickness of the semiconductorwafer 300 is removed from the backside 300 b thereof. Referring to FIGS.8C-8D, the carrier substrate 600 is thinned after a packaging layer 500is disposed thereon, and then a passivation layer 640 and conductivebumps 650 are formed in sequence. However, in another embodiment, theinsulating layer 630 is not removed but left intact during the thinningprocess of the carrier substrate 600. In other embodiments, theinsulating layer 630 is formed by semiconductor processing steps such asa thermal oxidation and chemical vapor deposition step. Alternatively,the insulating layer is formed by combing two wafers together, using awafer bonding process, wherein one of the wafers is provided with aninsulating layer.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A chip package, comprising: a semiconductor substrate having oppositefirst and second surfaces; a conductive pad structure disposed on thefirst surface of the semiconductor substrate; a heavily doped regionunderlying and electrically connected to the conductive pad structure;and a conductive feature underlying the heavily doped region andelectrically connected to the conductive pad structure through theheavily doped region.
 2. The chip package as claimed in claim 1, whereinthe conductive feature comprises a conductive bump, a conductivepattern, or combinations thereof.
 3. The chip package as claimed inclaim 1, further comprising an opening penetrating into thesemiconductor substrate from the second surface thereof to expose theheavily doped region; wherein the conductive feature comprises aconductive pattern in the openings to electrically connect to theheavily doped region.
 4. The chip package as claimed in claim 3, whereinthe conductive pattern extends into the heavily doped region.
 5. Thechip package as claimed in claim 4, wherein the conductive pattern inthe opening is isolated from the semiconductor substrate by aninsulating layer.
 6. The chip package as claimed in claim 1, wherein thesubstrate further comprises at least one bond pad region, and at leastone device region, wherein the conductive pad structure is disposed onthe bond pad region.
 7. The chip package as claimed in claim 6, furthercomprising: a packaging layer bonded to the semiconductor substrate; aspacer surrounding the device region and disposed between thesemiconductor substrate and the packaging layer to form a cavitytherebetween.
 8. The chip package as claimed in claim 1, furthercomprising a plurality of heavily doped regions isolated from oneanother by an insulating wall.
 9. The chip package as claimed in claim8, further comprising an insulating layer below the heavily dopedregions, wherein the insulating wall extends to the insulating layer.10. The chip package as claimed in claim 1, wherein the area of theheavily doped region is wider than that of the conductive pad structure.11. The chip package as claimed in claim 1, wherein the heavily dopedregion is disposed in a carrier substrate which is bonded to the firstsurface of the semiconductor substrate.
 12. The chip package as claimedin claim 11, wherein the carrier substrate is a silicon-on-insulatorsubstrate.
 13. A method for fabricating a chip package, comprising:providing a semiconductor wafer having opposite first and secondsurfaces, wherein the semiconductor wafer comprises a conductive padstructure on the first surface; forming a heavily doped regionunderlying the conductive pad structure, wherein the heavily dopedregion is electrically connected to the conductive pad structure; andforming a conductive feature underlying the heavily doped region,wherein the conductive feature is electrically connected to theconductive pad structure through the heavily doped region.
 14. Themethod as claimed in claim 13, wherein the step of forming theconductive feature comprises forming a conductive bump, a conductivepattern, or combinations thereof.
 15. The method as claimed in claim 13,further comprising: forming an opening penetrating into thesemiconductor substrate from the second surface thereof to expose theheavily doped region; wherein the step of forming the conductive featurecomprises forming a conductive pattern in the openings to electricallyconnect to the heavily doped region.
 16. The chip package as claimed inclaim 15, wherein the conductive pattern extends into the heavily dopedregion.
 17. The method as claimed in claim 15, further comprisingforming an insulating layer in the openings to isolate the conductivepattern from the semiconductor wafer.
 18. The method as claimed in claim13, wherein the substrate further comprises at least one bond padregion, and at least one device region, wherein the conductive padstructure is disposed on the bond pad region.
 19. The method as claimedin claim 18, further comprising: bonding a packaging layer to thesemiconductor wafer, wherein a cavity surrounded by a spacer is formedbetween the packaging layer and the semiconductor wafer.
 20. The methodas claimed in claim 13, further comprising forming a plurality ofheavily doped regions and an insulating wall therebetween the heavilydoped regions to isolate the heavily doped regions from one another. 21.The method as claimed in claim 20, further comprising forming aninsulating layer below the heavily doped regions, wherein the insulatingwall extends to the insulating layer.
 22. The method as claimed in claim13, wherein the area of the heavily doped region is wider than that ofthe conductive pad structure.
 23. The method as claimed in claim 13,wherein the step of forming the heavily doped region comprises forming aplurality of heavily doped regions in a carrier substrate, and themethod further comprises bonding the carrier substrate to the firstsurface of the semiconductor wafer.
 24. The method as claimed in claim23, wherein the carrier substrate is a silicon-on-insulator substrate.25. The method as claimed in claim 23, further comprising forming aninsulating wall to isolate the heavily doped regions from one another,wherein the step of forming the insulating wall comprises: forming aplurality of openings from a first surface of the carrier substrate;forming an insulating layer in the openings of the carrier substrate;and polishing the carrier substrate from a second surface opposite tothe first surface of the carrier substrate, to thereby form theinsulating wall to isolate the heavily doped regions.
 26. The method asclaimed in claim 25, further comprising bonding a packaging layer to thesemiconductor wafer, wherein the step of the forming the insulating wallis performed after the bonding of the packaging layer.
 27. The method asclaimed in claim 13, further comprising dicing the semiconductor waferto form a plurality of individual chip packages.